Arizona’s attorney general on Tuesday filed the first lawsuit challenging the Biden administration's new mandate for most U.S. workers to get vaccinated against COVID-19, calling the upcoming emergency rule an unconstitutional exercise of "unbridled power."

The complaint argues that President Joe Biden's directive instructing the U.S. Department of Labor's Occupational Safety and Health Administration (OSHA) to adopt and enforce the rule exceeds his executive authority and violates the Constitution’s equal protection clause through discrimination. As announced, the rule requires U.S. workers to get vaccinated but does not specifically require undocumented immigrants crossing the border to get inoculated.

“The executive branch has adopted an unconstitutional policy of favoring aliens that have unlawfully entered the United States over actual U.S. citizens, both native and foreign born,” the lawsuit states.

“Their rights to choose to be vaccinated — or not — command the unadulterated respect of defendants,” the lawsuit states. “Those of U.S. citizens: not so much.”

Biden’s new, yet-to-be-seen rule, called an emergency temporary standard, is expected to apply specifically to private sector U.S. employers with more than 100 workers once OSHA adopts it. Workers will be required to either get vaccinated or submit to weekly testing for COVID-19.

The rule is projected to affect approximately 100 million U.S. workers and about two-thirds of U.S. employees, according to the White House. Federal employers and contractors would be required to get vaccinated, with no testing option alternative. If the rule is issued as announced by Biden on Thursday, workers will be required to comply, or risk losing their jobs.

During a press call Tuesday evening, Arizona Attorney General Mark Brnovich said the mandate violates constitutional principles of federalism and separation of powers by overstepping the states’ rights to manage public health, safety, and welfare.

“It’s an unprecedented attempt by the federal government to impose something on the American people that clearly is not among the president’s enumerated powers,” Brnovich said.

Brnovich also claimed that Ronald Klain, the president's chief of staff, recognized the federal government's lack of authority to directly impose a mandate in his retweet of MSNBC anchor Stephanie Ruhle's post characterizing the move as a "work-around."

The lawsuit goes on to say that the Department of Homeland Security offers vaccination to non-U.S. citizens apprehended for unlawfully entering the U.S., though does not insist that they be vaccinated.